It sometimes takes a few days for the netipot to take effect. Also, be sure you use boiled (then cooled obviously) or distilled water to prevent organisms. Also, invert yourself after use, like bending over or doing a handstand and blowing out through your nose, to prevent sinus infection.

I don't have allergies either, however I do get blocked tubes from time to time, and I have learned that I have sensitivities to various environmental things that cause blocked ears. This is especially critical for me, as I'm a musician and I need to use my ears for a living.

Environmental causes that bother me are:

Cigarette smoke
Certain dogs (after days of exposure)
Many different perfumes and colognes
Scents in hair products and shampoos (Castor oil is usually the culprit and is in most men's hair styling products)
Scents in laundry soaps (try scent free for a while)
wool

You can try eliminating these one by one and see what works. It can take a few days or weeks after limiting exposure for the ears to clear up.

Blowing while pinching the nostrils is not generally a good idea. This will only push the obstructing material further back in the tube toward the middle ear space, not a very desirable outcome. Netipot is a better idea.

Sit and place your elbows on a table. With your thumb and index finger, gently but firmly grasp your lower ear where it attaches to your head. Pull outwards on both ears, then allow your head to hang down towards the table as though reading a book.

Check yourself and allow your arms and body to be in a relaxed state. As long as you don't force anything, you won't injure yourself.